Electro-optic modulation of multiple phase modulator waveguides with a single electrode

Abstract

Electro-optic modulation of multiple phase modulator waveguides with a single electrode is made possible by determining places of equal electric field strength. Substrate extensions support edges of a wide hot electrode and ground electrodes equally spaced from the wide hot electrodes. Waveguides are positioned in the extensions separated from the electrodes by buffer layers. A wide microstrip hot electrode on a buffer layer, wider substrate and ground has multiple waveguides in the substrate below the buffer layer. A thinned substrate has a microstrip hot electrode and spaced coplanar grounds with multiple waveguides located on both sides. Decreasing substrate thickness flattens the electric field strength between the electrodes and allows multiple waveguides located between the central hot and outer ground electrodes. Adjacent waveguides with different asymmetric waveguide index portion staged along their length eliminate cross talk.

We claim: 
     
       1. Apparatus comprising an electro-optic, multi-channel phase modulator of multiple phase optical waveguides configured for similar optical broadening of optical transmissions in multiple optical waveguides;
 the electro-optic, multi-channel phase modulator further comprising: 
 an lithium niobate substrate with a thickness of less than 10 microns; and 
 an electrode structure; 
 the electrode structure comprising: 
 a hot electrode positioned on the electro-optic material substrate; 
 at least one ground electrode positioned on the electro-optic material substrate; and 
 multiple optical waveguides positioned and evenly spaced on or in the electro-optic material substrate; 
 wherein the ground electrode is relatively narrower than the hot electrode; 
 a source adapted for providing an electric wave form applied to the electrode structure; 
 thereby providing an electric field having varied magnitudes; 
 the electric field having multiple locations of similar electric field magnitudes; 
 the multiple optical waveguides being positioned at the multiple locations of the similar electric field magnitudes, wherein the waveguides have a center-to-center spacing sufficient to prevent optical coupling between waveguides. 
 
     
     
       2. The apparatus of  claim 1 , comprising two ground electrodes wherein the two ground electrodes are each relatively narrower than the hot electrode, and are equally spaced laterally from the hot electrode. 
     
     
       3. The apparatus of  claim 2 , wherein the width of the hot electrode is narrower than the center-to-center waveguide spacing. 
     
     
       4. The apparatus of  claim 1 , wherein the ground electrodes are spaced at least one waveguide center-to-center spacing from the edge of the hot electrode. 
     
     
       5. The apparatus of  claim 1 , wherein the substrate has central parallel ridges supporting the edges of the hot electrode and the substrate has outer parallel ridges supporting the ground electrodes, and wherein first and second optical waveguides are mounted in the central parallel ridges, and third and fourth optical waveguides are mounted in the outer parallel ridges near the ground electrodes. 
     
     
       6. The apparatus of  claim 5 , further comprising first and second buffer layers positioned between the hot electrode and the first and second optical waveguides, and third and fourth buffer layers positioned between the ground electrodes and the third and fourth optical waveguides. 
     
     
       7. The apparatus of  claim 1 ,
 wherein the substrate extends between the electrode and the ground electrode; 
 and wherein the multiple optical waveguides are mounted within the substrate between the hot electrode and the ground electrode; 
 and further comprising a buffer layer which extends between the multiple optical waveguides and the hot electrode. 
 
     
     
       8. The apparatus of  claim 7 , wherein the hot electrode is a microstrip electrode. 
     
     
       9. The apparatus of  claim 1 , wherein the electrodes are disposed directly on the substrate. 
     
     
       10. The apparatus of  claim 1 , wherein lithium niobate substrate is about 5 microns thick. 
     
     
       11. A method comprising providing an electro-optic, multi-channel phase modulator of multiple phase optical waveguides configured for similar optical broadening of optical transmissions in multiple optical waveguides;
 providing lithium niobate substrate with a thickness of less than ten microns on the electro-optic, multi-channel phase modulator further comprising: 
 providing an electrode structure in or on the substrate, wherein providing the electrode structure further comprises providing a hot electrode positioned on the substrate; 
 providing at least one ground electrode positioned on the substrate and spaced away from the hot electrode, wherein the ground electrode is relatively narrower than the hot electrode; 
 providing multiple optical waveguides positioned on or in the substrate; 
 positioning each optical waveguide near the hot electrode or near the at least one ground electrode; 
 providing an electric wave form, applying the electric wave form to the electrode structure in or on the substrate, 
 thereby providing an electric field having varied magnitudes; 
 providing multiple locations of similar electric field magnitudes; and 
 positioning the multiple optical waveguides at the multiple locations of the similar electric field magnitudes. 
 
     
     
       12. The method of  claim 11 , wherein the ground electrodes are placed equidistant laterally from the hot electrode. 
     
     
       13. The method of  claim 12 , wherein the optical waveguides are evenly positioned on or in the substrate. 
     
     
       14. The method of  claim 13 , further comprising positioning first and second optical waveguides near edges of the hot electrode, and third and fourth optical waveguides near the relatively narrow ground electrodes. 
     
     
       15. The method of  claim 14 , further comprising providing inner parallel ridges of the lithium niobate substrate inner parallel ridges supporting edges of the hot electrode on the inner parallel ridges and the electro-optic material substrate, providing outer parallel ridges on the electro-optic material substrate and supporting the ground electrodes on the outer parallel ridges and mounting first and second optical waveguides in the inner parallel ridges near the edges of the hot electrode, and mounting third and fourth optical waveguides in the outer parallel ridges near the ground electrodes, and further comprising providing buffer layers between the edges of the hot electrode and the first and second optical waveguides, and third and fourth buffer layers positioned between the ground electrodes and the third and fourth optical waveguides. 
     
     
       16. The method of  claim 11 , further comprising providing the optical waveguides at the locations of the similar electrical field magnitudes. 
     
     
       17. The method of  claim 11 ,
 wherein the providing the electro-optical material substrate comprises extending the electro-optical material substrate between the hot electrode and the ground electrode; 
 and wherein the providing the multiple optical waveguides comprises mounting the multiple optical waveguides within the electro-optical material substrate between the hot electrode and the ground electrode, and closer to the hot electrode; 
 and further comprising providing a buffer layer extending between the multiple optical waveguides and the hot electrode. 
 
     
     
       18. The method of  claim 17 , wherein the providing the hot electrode comprises providing a microstrip electrode. 
     
     
       19. The method of  claim 18 , wherein widening of the microstrip electrode providing increasing possible numbers of the multiple optical waveguides. 
     
     
       20. The method of  claim 11 , wherein the providing of the electro-optic material substrate comprises providing a 5 microns-thin electro-optic material substrate, wherein providing the hot electrode comprises providing a microstrip hot electrode, and providing the at least one ground electrode comprises providing two microstrip ground electrodes, and providing one microstrip ground electrode on either side and coplanar with the microstrip hot electrode, thereby avoiding any variance of the electric field strength between the microstrip hot electrode and the two microstrip ground electrodes, and increasing numbers of optical waveguides that may be used there between.